Twisted wire pairs are widely used in electrical equipment for numerous reasons including the elimination of electrical interference, and providing more compact and easily identifiable wiring arrangement in complicated circuits and wire harnesses. Because of the extensive use of twisted wire pairs it has become desirable to have highly productive means for preparing large numbers of wire pairs which are cut to predetermined lengths and which have the insulation stripped from one or both ends of each wire of the pair. It is particularly desirable to have means which can automatically prepare wire pairs cut to predetermined lengths with insulation stripped from one or both ends and which can operate in conjunction with automatic or semi-automatic circuit wiring machines.
Known methods for preparing twisted wire pairs with insulation stripped from the wire ends include entirely manual operations using hand-held tools. Furthermore, U.S. Pat. Nos. 3,779,290 and 3,815,449 disclose apparatus for stripping insulation from one end of a wire pair and wherein the wire pair is manually inserted in the apparatus. U.S. Pat. No. 3,827,465 discloses apparatus which prepares individual wires of predetermined length and twists the wires together after the insulation is stripped.
The present invention is directed to apparatus which will automatically and continuously prepare predetermined lengths of twisted wire pairs which have insulation stripped from opposite ends of one or both wires of the wire pair. Such apparatus according to the present invention is operable to prepare preselected lengths of twisted wire pairs from a substantially continuous and uncut supply such as a large spool of pretwisted wire.
The apparatus of the present invention also provides improved means for clamping the twisted wire pair and untwisting the wires of the pair in the section of wire that is to form the end portions of the wire leads whereby the insulation may then be cut and stripped automatically. The untwisting mechanism included in the present invention is operable to impart a controlled amount of untwist to a portion of the twisted wire pair whereby the wires of the pair may be cut and have a predetermined length of insulation stripped from the wire ends formed by the cut.
The apparatus of the present invention further provides improved mechanism for positioning an untwisted portion of a twisted wire pair whereby the insulation on the untwisted portion may be accurately cut without unwanted cutting or scratching of the conductor wire and without ripping or tearing the insulation at the insulation cut. The improved wire positioning mechanism of the present invention includes plural cams cooperable with mechanism for actuating insulation cutting blades whereby the untwisted portion 1 of the wire pair is properly positioned for accurately cutting the insulation without damaging the conductor wire.
The apparatus of the present invention provides improved means for producing twisted wire pair of predetermined length with insulation stripped from the wire ends and which is adapted to be operated in conjunction with automatically controlled wire connecting machinery or for other applications where large quantities of twisted wire pairs are needed .